Infrared photodetectors based on multiwalled carbon nanotubes: Insights into the effect of nitrogen doping

Abstract

Multiwalled carbon nanotubes (MWCNTs) and their nitrogen-doped counterparts (N-MWCNTs) were synthesized by the pyrolysis technique. For infrared detection, Ag-MWCNTs-Ag structured devices have been fabricated and their infrared photoresponses are assessed. The devices show stable photoresponses over multiple cycles. The observed responsivity values of the devices are in the range of 0.2–0.4 AW−1 (at a low bias voltage of 0.5 V) and are superior to many other infrared detectors using similar materials. In both the devices, the photocurrents originate predominantly due to photoconductive effect of the semiconducting MWCNTs. External quantum efficiency (EQE) of the N-doped MWCNTs based device is much higher than that of the undoped one. The better performance of the N-doped MWCNTs based device is due to higher infrared absorption and trap assisted gain influenced by the band structure modification of the nanotubes by doped heteroatoms.